1. Field of the Invention
The present invention relates to a method and an apparatus for plasma processing such as dry etching, sputtering, plasma CVD, or the like utilized for manufacturing electronic devices and micromachines of a semiconductor or the like, and more particularly to the method and apparatus which utilize plasma excited with the use of a VHF or UHF-band high frequency power.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. 8-83696 describes that it is important to make use of high-density plasma to cope with finely forming electronic devices of a semiconductor or the like. In the meantime, low electron temperature plasma having a high electron density and a low electron temperature is attracting attention these days.
When a gas having a strong negative characteristic, in other words, easy to generate negative ions such as Cl2, SF6, or the like is turned to plasma and an electron temperature becomes approximately 3 eV or lower, a larger quantity of negative ions is generated than when the electron temperature is high. Utilizing this phenomenon can prevent an abnormality in shape in a type of etching called xe2x80x9cnotchxe2x80x9d which is caused by positive charges piled to a bottom part of a fine pattern due to an excessive injection of positive ions, thus enabling highly accurate etching into remarkably fine patterns.
When a gas including carbon and fluorine such as CxFy, CxHyFz (x, y and z are natural numbers) or the like generally used to etch insulating films such as silicon oxide films or the like is turned to plasma, and if the electron temperature becomes approximately not higher than 3 eV, dissociation of the gas is restricted more than when the electron temperature is high, particularly, generation of F atoms, F radicals, and the like is suppressed. Since the F atoms, F radicals, and the like can be used to etch silicon fast, the insulating films can be etched with a higher etching selectivity to silicon as the electron temperature is lower.
A temperature of ions and a potential of plasma decrease when the electron temperature becomes not higher than 3 eV, so that ionic damage to substrates in plasma CVD can be reduced.
It is a plasma source using a VHF or UHF-band high frequency power that has received the most-recent attention as a technique to generate plasma of a low electron temperature.
FIG. 10 is a sectional view of a plasma processing apparatus of a plate-shaped antenna system. In FIG. 10, a vacuum chamber 101 is evacuated by a pump 103 as an evacuation device while a predetermined gas is introduced from a gas supply device 102 into the vacuum chamber 101. With the inside of the vacuum chamber 101 kept at a predetermined pressure, a high frequency power of 100 MHz is supplied from a high frequency power source 104 for antenna to an antenna 105. In consequence, plasma is generated in the vacuum chamber 101, processing a substrate 107 placed on a substrate electrode 106, for example, by etching, deposition, surface reforming, or the like manner. At this time, a high frequency power is also supplied from a high frequency power source 108 for substrate electrode to the substrate electrode 106 as shown in FIG. 10, whereby an ion energy reaching the substrate 107 can be controlled. The antenna 105 consists of a metallic plate 109 of a radius of 115 mm and a dielectric plate 110 of a radius of 115 mm, and is designed to supply a high frequency voltage to the metallic plate 109 via a through hole 111 formed near the center of the dielectric plate 110.
According to the prior art system shown in FIG. 10, it is difficult to obtain stable plasma of a high plasma density.
The present invention has for its object to provide a method and an apparatus whereby stable plasma of a high plasma density can be obtained, while eliminating the above-described issue in the prior art.
In accomplishing these and other aspects, according to a first aspect of the present invention, there is provided a plasma processing method comprising:
evacuating a vacuum chamber while supplying a gas into the vacuum chamber, thereby controlling an interior of the vacuum chamber to a pressure; and
supplying a high frequency power of a frequency of 50 MHz-3 GHz to an antenna which is set opposite to a substrate placed at a substrate electrode in the vacuum chamber and which has a structure with a dielectric member held between a wall face of the vacuum chamber opposite to the substrate and a metallic plate, thereby generating plasma inside the vacuum chamber and processing the substrate,
wherein the high frequency power is supplied to satisfy a relation 3r less than c/(fxc2x7∈xc2xd) less than 9r when c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member, and r is a half (m) of a longer line of a shape of the dielectric member.
According to a second aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein in supplying the high frequency power of the frequency of 50 MHz-3 GHz to the antenna, the high frequency power is supplied to satisfy a relation 3r less than c/(fxc2x7∈xc2xd) less than 9r when c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member, and r is a radius (m) of a circular shape of the dielectric member.
According to a third aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein in supplying the high frequency power of the frequency of 50 MHz-3 GHz to the antenna, the high frequency power is supplied to satisfy a relation 3r less than c/(fxc2x7∈xc2xd) less than 9r when c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member and, r is a half (m) of a diagonal line of a rectangular shape of the dielectric member.
According to a fourth aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein in supplying the high frequency power of the frequency of 50 MHz-3 GHz to the antenna, the high frequency power is supplied to satisfy a relation 3r less than c/(fxc2x7∈xc2xd) less than 9r when c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member and, r is a half (m) of a major axis of an ellipse shape of the dielectric member.
According to a fifth aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein in supplying the high frequency power of the frequency of 50 MHz-3 GHz to the antenna, the high frequency power is supplied to satisfy a relation 4r less than c/(fxc2x7∈xc2xd) less than 8r when c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member, and r is a half (m) of a longer line of a shape of the dielectric member.
According to a sixth aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein in supplying the high frequency power of the frequency of 50 MHz-3 GHz to the antenna, the high frequency power is supplied to satisfy a relation 5r less than c/(fxc2x7∈xc2xd) less than 7r when c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member, and r is a half (m) of a longer line of a shape of the dielectric member.
According to a seventh aspect of the present invention, there is provided a plasma processing method according to the first aspect, further comprising:
supplying a high frequency voltage to the metallic plate via a through hole formed in a vicinity of a center of the dielectric member; and
short circuiting the metallic plate and the wall face of the vacuum chamber opposite to the substrate via through holes formed at a plurality of points different from the center and a periphery of the dielectric member.
According to an eighth aspect of the present invention, there is provided a plasma processing method according to the seventh aspect, wherein in shortcircuiting the metallic plate and the wall face of the vacuum chamber opposite to the substrate, each of the points is shortcircuited to the vacuum chamber while each of the points is almost isotropically arranged to the center of the antenna.
According to a ninth aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein in supplying the high frequency power of the frequency of 50 MHz-3 GHz to the antenna, the high frequency power is supplied to the antenna while a surface of the antenna is covered with an insulating cover.
According to a 10th aspect of the present invention, there is provided a plasma processing apparatus comprising:
a vacuum chamber;
a gas supply device for supplying a gas into the vacuum chamber;
an evacuation device for evacuating the vacuum chamber;
a substrate electrode used for placing a substrate in the vacuum chamber;
an antenna in a structure having a dielectric member held between a wall face of the vacuum chamber opposite to the substrate electrode and a metallic plate; and
a high frequency power source capable of supplying a high frequency power of a frequency of 50 MHz-3 GHz to the antenna,
the plasma processing apparatus being constituted to supply the high frequency power to satisfy a relation 3r less than c/(fxc2x7∈xc2xd) less than 9r wherein c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member and, r is a half (m) of a longer line of a shape of the dielectric member.
According to an 11th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein the plasma processing apparatus being constituted to supply the high frequency power to satisfy a relation 3r less than c/(fxc2x7∈xc2xd) less than 9r wherein c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member, and r is a radius (m) of a circular shape of the dielectric member.
According to a 12th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein the plasma processing apparatus is constituted to supply the high frequency power to satisfy a relation 3r less than c/(fxc2x7∈xc2xd) less than 9r wherein c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member, and r is a half (m) of a diagonal line of a rectangular shape of the dielectric member.
According to a 13th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein the plasma processing apparatus is constituted to supply the high frequency power to satisfy a relation 3r less than c/(fxc2x7∈xc2xd) less than 9r wherein c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member, and r is a half (m) of a major axis of an ellipse shape of the dielectric member.
According to a 14th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein the plasma processing apparatus is constituted to supply the high frequency power to satisfy a relation 3r less than c/(fxc2x7∈xc2xd) less than 9r wherein c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member, and r is a half (m) of a major axis of an ellipse shape of the dielectric member.
According to a 15th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein the plasma processing apparatus is constituted to supply the high frequency power to satisfy a relation 5r less than c/(fxc2x7∈xc2xd) less than 7r wherein c is a light velocity (m/sec), f is a frequency (Hz) of the high frequency power, ∈ is a relative permittivity of the dielectric member, and r is a half (m) of a longer line of a shape of the dielectric member.
According to a 16th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein a high frequency voltage is supplied to the metallic plate via a through hole formed is a vicinity of a center of the dielectric member, thereby shortcircuiting the metallic plate and the wall face of the vacuum chamber opposite to the substrate via through holes formed at a plurality of points different from the center and a periphery of the dielectric member.
According to a 17th aspect of the present invention, there is provided a plasma processing apparatus according to the 16th aspect, wherein each of the points to be shortcircuited to the vacuum chamber is almost isotropically arranged to the center of the antenna.
According to an 18th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein a surface of the antenna is covered with an insulating cover.
According to a 19th aspect of the present invention, there is provided a plasma processing apparatus according to the 10th aspect, wherein a ring and groove-shaped plasma trap is set between the antenna and vacuum chamber.